The fan-throated lizard (Sarada superba) was first described last
year as endemic to the semi-arid plateaus of India’s Western Ghats. The species
weighs only 3–5g, fitting into the palm of your hand, and many live only a
year. Between February and March these compact reptiles turn from juveniles to
adults within a month and then they eat, fight and mate until the seasons
change.

Robotic lizards used to test colour-coded
messages

During their short summer breeding
season the males attract attention by sitting on rocks and flapping brightly coloured
flaps of skin beneath their jaw known as dewlaps. Daubed with orange, black and
iridescent blue patches, the colours communicate important information about their
health and aggression levels to potential female mates and male competitors.

Since lizards have eyes on either side
of their head, researchers Amod Zambre and Maria Thaker from the Centre for
Ecological Sciences at the Indian Institute of Science, Bangalore placed a live
lizard in a glass tank with robotic lizards on either side. They then tested different
colour combinations, recording which way the lizard turned, finding distinct
preferences based on gender.

Thaker says “differences in their
preferences for individual colours suggests that colours contain distinct
pieces of information”. Orange, usually made from a diet of yellow, orange or
red pigments known as carotenoids, probably helps the female assess the health
of males, their territory quality and foraging success.

Blue, however, has to
be made during a lizard’s sexual development, and may relate more to aggression
levels. Males also enhance this blue on their front, back and the sides of
their tails in male to male interaction.

Black, which is a very high-contrast
shade and thus often used to communicate important information, may also convey
information about aggression levels.